Effect of incubation temperature on zearalenone production by strains of Fusarium crookwellense.

After 6 weeks incubation on rice 2 strains of Fusarium crookwellense produced more zearalenone (6060-5010 mg/kg dry wt of culture) at ambient temperature (16-29 degrees C) in daylight than at ambient temperature (18-23 degrees C) in darkness or at controlled temperatures of 11 degrees C, 20 degrees C or 25 degrees C in darkness. Yields at 25 degrees C were low. Incubation at 11 degrees C during the second 3 weeks incubation increased yields only when preliminary incubation had been at 25 degrees C. After 6 weeks incubation at controlled temperatures in darkness, 4 strains produced most zearalenone at 20 degrees C (2460-21 360 mg/kg), 1 strain at 11 degrees C (6570 mg/kg). Yields at a temperature oscillating daily from 10-20 degrees C were less than at 15 degrees C. One of the 5 strains produced appreciable amounts of a-zearlaenol (1645 mg/kg at 20 degrees C) and 2 of nivalenol (340 and 499 mg/kg at 20 degrees C).     

The role of temperature in the regulation of the circadian rhythm of CO2 fixation in Bryophyllum fedtschenkoi

Detached leaves of Bryophyllum fedtschenkoi Hamet et Perrier kept in normal air show a single period of net CO₂ fixation on transfer to constant darkness at temperatures in the range 0–25 °C. The duration of this initial fixation period is largely independent of temperature in the range 5–20 °C, but lengthens very markedly at temperatures below 4 °C, and is reduced at temperatures above 25 °C. The onset of net fixation of CO₂ on transfer of leaves to constant darkness is immediate at low temperatures, but is delayed as the temperature is increased. The ambient temperature also determines whether or not a circadian rhythm of CO₂ exchange occurs. The rhythm begins to appear at about 20 °C, is most evident at 30 °C and becomes less distinct at 35 °C. The occurrence of a distinct circadian rhythm in CO₂ output at 30° C in the absence of a detectable rhythm in PEPCase kinase activity shows that the kinase rhythm is not a mandatory requirement for the rhythm of PEPCase activity. However, when it occurs, the kinase rhythm undoubtedly amplifies the PEPCase rhythm.Abbreviation PEPCase phosphoenolpyruvate carboxylase We thank the Agricultural and Food Research Council for financial support for this work.     

Effects of ambient Lake Mohave temperatures on development,oxygen consumption,and hatching success of the razorback sucker

Synopsis Spawning of razorback suckers,Xyrauchen texanus, in Lake Mohave occurred from 10–22°C and larvae were collected at water temperatures from 10–15°C in 1982 and 1983. In the laboratory, hatching success was similar from 12–20°C, but reduced hatching success was found at 10°C while none hatched a 8°C. Development rate and oxygen consumption were positively related to incubation temperature. Direct effects of ambient Lake Mohave water temperatures on hatching success of razorback sucker embryos are considered minimal. Historical spawning temperatures for the species are hypothesized based upon successful incubation temperatures and comparison to the white sucker,Catostomus commersoni.     

Biology of Ixodes Rubicundus Ticks under Laboratory Conditions: Observations on Oviposition and Egg Development

Observations on oviposition and egg development of Ixodes rubicundus were made under laboratory conditions. Engorged females were exposed to temperatures in the range 10–25°C and relative humidities (RHs) of 33 and 93%. The pre-oviposition period, oviposition period, incubation period, conversion efficiency index (CEI) values and fecundity were determined. The mean pre-oviposition period varied from 13.3 days (temperature 25°C and RH 33%) to 68.3 days (temperature 10°C and RH 93%). Oviposition extended from a mean of 39 days (temperature 25°C and RH 93%) to 201.7 days (temperature 10°C and RH 93%). The developmental zero temperature for the pre-oviposition period was 9.2°C. The mean total number of eggs produced by engorged I. rubicundus females varied from 2045.7 (temperature 10°C and RH 93%) to 3777.7 (temperature 20°C and RH 93%). Both female mass and RH significantly (p < 0.01) influenced the number of eggs produced. CEI values varied between 43.1–54.4% (RH 93%) and 34.1–42.5% (RH 33%). At 93% RH females produced between 14.2 and 17.7 eggs per mg body mass compared to the 13.2–14.6 eggs per mg body mass at 33% RH. The shortest mean incubation period recorded was 164.3 days (temperature 25°C and RH 93%). The developmental zero temperature for incubation was 6.5°C. Both the pre-oviposition and oviposition periods of I. rubicundus are more extended compared to other species of the genus. Ixodes rubicundus produces a large number of small eggs compared to other prostriate ticks.     

Effect of temperature on the ovipositional biology and egg viability of the cattle tickBoophilus annulatus (Acari: Ixodidae)

The effect of temperature on the ovipositional biology ofBoophilus annulatus (Say) was determined under laboratory conditions. Engorged females subjected to constant temperatures of 12 and 45°C died without ovipositing, while females held at 15 and 40°C laid eggs which did not hatch. The preoviposition period at 25–40°C was 2–3 days; however, significant increases occurred at 20°C (5.2 days) and at 15°C (16.3 days). The number of eggs laid per female was ca. 2700 at temperatures of 25–35°C, but decreased significantly at 20°C (ca. 2300 eggs/female), 15°C (ca. 1800 eggs/female), and at 40°C (ca. 300 eggs/female). No differences were observed in the Conversion Efficiency Index (CEI) values at temperatures of 20–30°C (ca. 50%), while temperatures of 15 and 40°C produced the lowest CEI values at 35.6 and 4.9%, respectively. Hatch-ability of eggs was ca. 80% at temperatures of 20–35°C. Incubation period of eggs ranged from 52.2 days at 20°C to 16.2 days at 35°C. The thermal threshold for egg development determined by linear regression was 12.9°C. Females subjected to four fluctuating temperature regimes produced no differences in number of eggs/female (ca. 2400), CEI (ca. 50%), or hatchability of eggs (ca. 75%). Preoviposition period and incubation were significantly affected by a change in the thermoperiod, becoming longer in duration as the temperatures were decreased. From studying females exposed for various intervals from 0 to 105 days at 12°C, indications were that the longer the exposure period the more adverse the effects were on oviposition and egg-hatch. Correspondingly, exposure of eggs to a temperature of 15°C for up to 105 days gave indications that the longer the eggs remained at 15°C, the lower the hatch would be after transfer back to a temperature of 25°C.     

Effects of temperature on the darkness survival of marine microplanktonic algae

Thirty-seven species of marine microplanktonic algae from 10 taxonomic classes were tested for their viability in axenic culture after prolonged exposure to darkness at 2°, 10°, and 20°C. The darkness test periods were prolonged in weekly installments up to a maximum of 1 year, and viability retention (survival) was judged from the capability for resuming growth after replacement in light. The 2°C-tests showed 32% of the species reaching the limits of survival with 5–6 months of darkness exposure, but another similar percentage continued to tolerate darkness for double this period. These darkness toleration limits were considerably shorter at 20°C for the strains known to be isolated from cold marine regions, whereas the warm-water strains showed the reverse temperature effect in surviving significantly longer at 10°–20°C than at 2°C. Irrespective of temperature or algal class, the bulk of the more resistant survivors was formed by the strains qualifying as benthic types, about 70% of which tolerated 11–12 months and the rest at least 5–6 months of darkness. A few randomly chosen benthic strains extended this toleration to 3 years of darkness. It was concluded that phytoplankters retain darkness-endurance capacity determined by their ecological origin and with no obvious taxonomic correspondence. The concept of ecological races, characterized by temperature control of darkness survival, is discussed.The termdarkness-survival is used throughout this report to denote the retention of cellular viability by an algawithout growth (i.e., without significant increase in cellular mass or numbers) during exposure to darkness. Implicit in this definition is the denial of any known possibility of growth, either autotrophic requiring light or heterotrophic requiring organic-carbon, since both these agents are effectively absent in the survival cases considered here.     

Synchronous Crepuscular Flight of Female Asian Gypsy Moths: Relationships of Light Intensity and Ambient and Body Temperatures

Female gypsy moths (Lymantria dispar) of Asian heritage studied in central Siberia and Germany exhibit a highly synchronous flight at dusk, after light intensity falls to about 2 lux. This critical light intensity sets the timing of flight behaviors independent of ambient temperature. Flight follows several minutes of preflight wing fanning during which females in Germany and those from a laboratory colony (derived from Siberian stock) raised their thoracic temperatures to 32–33°C at ambient temperatures of 19–22°C. Thoracic temperature of females in free flight exceeded the air temperature (19–22°C) by approximately 11–13°C. The duration of wing fanning was strongly dependent on ambient temperature. In Germany, where ambient temperatures at dusk ranged between 21 and 25°C, females wing fanned for only 2.1 ± 0.2 (SE) min; in the much colder temperatures prevalent at dusk in Bellyk, central Siberia (11–13°C), females spent 11.2 ± 0.6 min in preflight wing fanning. The majority (80%) of mated and even virgin females initiated flight during the evening of the day they eclosed. However, in Bellyk, a small proportion (12%) of females wing fanned for an extended time but then stopped, whereas others (8%) never wing fanned and, therefore, did not take flight. Females also were capable of flight when disturbed during the daylight hours in Germany where the maximal temperature was high (27–30°C), but not in Siberia, where temperatures peaked at only 17–19°C. However, Siberian females were able to propel themselves off the tree on which they were perched by executing several vigorous wing flicks when approached by the predaceous tettigoniid, Tettigonia caudata.     

SelectingRhizobium phaseoli strains for use with beans (Phaseolus vulgaris L.) in Kenya: Tolerance of high temperature and antibiotic resistance

Forty one strains ofRhizobium phaseoli were screened for the ability to multiply at high temperatures on yeast extract-mannitol agar. Most strains were tolerant of 30°C, eight strains were tolerant of 45°C and two of 47°C although the rate of multiplication was reduced at 45–47°C. The high temperature-tolerant strains were isolated from Kenyan soils and were fast-growing. Seven of the eight strains tolerant of 45–47°C lost their infectiveness after incubation at high temperature but four strains tolerant of 40°C remained infective after incubation at that temperature.Thirty six strains were resistant to 200 g ml^–1 streptomycin sulphate and 29 strains to 200 g ml^–1 spectinomycin dihydrochloride. Eight strains were resistant to both antibiotics each at 200 g ml^–1. Two of the double-labelled antibiotic-resistant mutants lost their infectiveness onPhaseolus vulgaris. The response to acidity was unaltered and two of the mutants showed a decrease in temperature tolerance. The doublelabelled mutants were recoverable from two Kenyan soils.     

Degradation of phenol and toxicity of phenolic compounds: a comparison of cold-tolerant<Emphasis Type="Italic"> Arthrobacter</Emphasis> sp. and mesophilic<Emphasis Type="Italic"> Pseudomonas putida</Emphasis>

Phenol degradation efficiency of cold-tolerant Arthrobacter sp. AG31 and mesophilic Pseudomonas putida DSM6414 was compared. The cold-tolerant strain was cultivated at 10°C, while the mesophile was grown at 25°C. Both strains degraded 200 mg and 400 mg phenol/l within 48–72 h of cultivation, but the cold-tolerant strain produced more biomass than the mesophile. Both strains oxidized catechol by the ortho type of ring fission. Catechol 1,2 dioxygenase (C1,2D) activity was found intra- and extracellularly in the absence and in the presence of phenol. In the presence of 200 mg phenol/l, C1,2D activity of the mesophile was about 1.5- to 2-fold higher than that of the cold-tolerant strain. However, an initial phenol concentration of 400 mg/l resulted in a comparable enzyme activity of the cold-tolerant and the mesophilic strain. The two strains differed significantly in their toxicity pattern towards 12 aromatic (mostly phenolic) compounds at different growth temperatures, which was determined via growth inhibition in the presence of nutrients and toxicants. For the cold-tolerant strain, toxicity was significantly lower at 10°C than at 25°C. The mesophile showed a significantly lower susceptibility to high hydrocarbon concentrations when grown at 25°C compared to 10°C.Communicated by K. Horikoshi     

Development of sweating ability in winter- and summer-born Friesian calves aged 1 to 6 weeks

Sweating rate, rectal and skin temperatures and respiration rate were measured at weekly intervals from 7 days of age (for 4 weeks in Experiment 1; 6 weeks in Experiment 2) in winter- and summer-born Friesian calves exposed to a temperature of 39°C dry bulb and 32°C wet bulb in a climate chamber. Four calves were studied in each season in both experiments. In Experiment 1, ambient temperatures were from 3° to 9°C higher in early summer than in late winter. During each 39°C exposure, sweating rate increased from basal levels of 40–90 to plateau levels of 120–300 g/m² per h after 90–120 min. The increase in sweating rate with age was most pronounced in winter-born calves, but summer-born calves had higher values at 1 week of age (167±52.4 vs 94.4±30.1 g/m² per h). Seasonal differences in ambient temperature were greater in Experiment 2 (11° to 17°C). In this case summer-born calves had higher sweating rates at each age (plateau values of 220–320 g/m² per h), and showed a more rapid increase in sweating rate during each 39°C exposure than winter-born calves (plateau values of 100–250 g/m² per h). The results demonstrate major changes in sweating competence during the first 4–6 weeks of life in Friesian calves, a quite pronounced effect of season (ambient temperature) on the levels of sweating achieved, and indicate that low sweating rates in newborn calves are a contributing factor in deaths due to hyperthermia in semi-arid grazing areas.     

Responsiveness of Orobanche ramosa L. Seeds to GR 24 as Related to Temperature, Oxygen Availability and Water Potential During Preconditioning and Subsequent Germination

Broomrape (Orobanche ramosa L.) is a root holoparasite responsible for important yield losses in numerous crops, particularly in the Mediterranean area. In this paper, the effects of temperature, oxygen concentration and water potential of the medium on broomrape seed germination were investigated. Seeds became able to germinate in the presence of a strigol analogue (GR 24) only after a preincubation period for at least 3 days at 20 °C. Their responsiveness to GR 24 increased with increasing duration of their preconditioning at 20 °C, and was optimal after 2–3 weeks. The preconditioning treatment was effective at temperatures ranging from 10 to 30 °C. At the optimal temperature (20 °C), it required at least 1% oxygen in the atmosphere and remained effective at a water potential of the medium of –2 MPa. A too prolonged preincubation of seeds at sub- or supraoptimal temperatures (5 and 30 °C) resulted in induction of a secondary dormancy. Seeds preconditioned for 14 days at 20 °C germinated in the presence of 1 mg L^–1 GR 24 at temperatures ranging from 10 to 25 °C, and the thermal optimum was the same (20 °C) than that of preconditioning. At 20 °C, seeds were able to germinate in the presence of GR 24 under atmospheres containing at least 3% oxygen and at a water potential of the medium as low as –3 MPa. The differences observed in the effects of environmental factors on preconditioning efficiency and germination of preconditioned seeds suggest that both processes involve different mechanisms. The results obtained might also help to better understand the regulation of O. ramosa spread in temperate areas.     

Effects of light and temperature on sporangiophore initiation in Pilobolus crystallinus (Wiggers) Tode

Sporangiophore initiation in Pilobolus crystallinus grown in white light was induced by either a dark or a low-temperature treatment. The period of darkness necessary to induce sporangiophore initiation was shortened by lowering the temperature. Arrhenius plots for the sporangiophore-suppressing reaction in both light and darkness consisted of two straight lines with a Q₁₀ of about 2 at lower temperatures and 8–11 at higher temperatures. The temperature at which the Q₁₀ changed was the lower, the higher the fluence rate: 14° C at 8 W/m², 19.5° C at 0.24 W/m² and 24.5° C in darkness. Possible interpretations of these results are briefly presented.Abbreviations %SP percentage of trophocysts initiating sporangiophores - D50% duration of treatment required to 50% sporangiophore initiation     

Response of Douglas fir seedlings to phosphorus fertilization and influence of temperature on this response

Summary Effects of P fertilizers on growth of Douglas fir (Pseudotsuga menziesii var.menziesii (Mirb.) Franco.) seedlings were examined in pots and nursery beds. In pot experiments levels of P equivalent to 300 kg/ha were adequate for maximum growth over 14–18 weeks and resulted in available soil P levels of 80 ppm after 15 weeks' growth. Maximum growth in pots was obtained with shoot P concentrations of 0.18%–0.20%, with higher values at lower temperatures, but the optimum concentration for one-year old (1-0) nursery seedlings was 0.16% P. Growth of seedlings was greatly restricted at a soil temperature of 5°C and an air temperature of 12°C. At a soil temperature of 10°C and an air temperature of 14°C seedling P requirement was greater than at soil and air temperatures of 20°C.Comparison showed that monammonium phosphate was more effective than calcium superphosphate in stimulating growth in pots and nursery. Triple superphosphate was also effective in the nursery. Diammonium phosphate, potassium dihydrogen phosphate and phosphoric acid had no advantages as P sources in the nursery. Available P levels of 100–130 ppm, in the loamy sand and sandy loam nurseries studied, and needle P concentrations of 0.18%, when sampled in October, were associated with maximum growth of two-year old (2-0) seedlings.P fertilization decreased root/shoot ratio, but did not alter the allometric relationship of shoot to root. Improving P status from a low level increased root growth capacity in 2-0 seedlings and P fertilization of potted seedlings increased dry weight/height ratio. Uptakes per seed bed ha of 236 kg N, 31 kg P, 81 kg K and 73 kg Ca by 2-0 seedlings were comparable with, or greater than, uptake rates of agricultural crops. Recoveries of 6–11% of P from fertilizer were recorded in the nursery.     

Effect of acute pH depression on the survival of the freshwater amphipod Hyalella azteca at variable temperatures: field and laboratory studies

Field observations on temperature and pH of a small pond showed that a amphipod population of Hyalella azteca was exposed to variable seasonal pH between 5.10–5.85, and water temperatures between 2–21 °C. Laboratory experiments were designed to simulate seasonal temperatures and field pHs of a small pond habitat. Laboratory bioassay experiments were conducted to determine the survival of Hyalella azteca at pHs 4, 5, 6 and 7, and varying temperatures of 5°, 10°, 15°, 20° and 25 °C.The LT₁₀₀ at pH 4 and 25 °C was 5.7 ± 0.47 days, compared to 47.3 ± 2.49 days at 5 °C. An Analysis of Variance (ANOVA) showed temperature was a significant (p > 0.0001) source of variation in the acute lethality of pH to H. azteca. A Duncans Multiple Range Test (DMRT) further showed that in laboratory experiments at pH 4, there was a significant difference ( = 0.01) between the LT_100s at 5°, 10°, 15° and 20 °C, but not between temperatures 20° and 25 °C.     

Root-zone temperature and salinity: Interacting effects on tillering,growth and element concentration in barley

The effects of root-zone salinity (0, 30, and 60 mmol L^–1 of NaCl) and root-zone temperature (10, 15, 20, and 25°C) and their interactions on the number of tillers, total dry matter production, and the concentration of nutrients in the roots and tops of barley (Hordeum vulgare L.) were studied. Experiments were conducted in growth chambers (day/night photoperiod of 16/8 h and constant air temperature of 20°C) and under water-culture conditions. Salinity and root temperature affected all the parameters tested. Interactions between salinity and temperature were significant (p<0.05) for the number of tillers, growth of tops and roots, and the concentration of Na, K, P in the tops and the concentration of P in the roots. Maximum number of tillers and the highest dry matter were produced when the root temperature was at the intermediate levels of 15 to 20°C. Effect of salinity on most parameters tested strongly depended on the prevailing root temperature. For example, at root temperature of 10°C addition of 30 mmol L^–1 NaCl to the nutrient solution stimulated the growth of barley roots; at root temperature of 25°C, however, the same NaCl concentration inhibited the root growth. At 60 mmol L^–1, root and shoot growth were maximum when root temperature was kept at the intermediate level of 15°C; most inhibition of salinity occurred at both low (10°C) and high (25°C) root temperatures. As the root temperature was raised from 10 to 25°C, the concentration of Na generally decreased in the tops and increased in the roots. At a given Na concentration in the tops or in the roots, respective growth of tops or roots was much less inhibited if the roots were grown at 15–20°C. It is concluded that the tolerance of barley plant to NaCl salinity of the rooting media appears to be altered by the root temperature and is highest if the root temperature is kept at 15 to 20°C.     

Thoracic temperature,shivering, and flight in the monarch butterfly,Danaus plexippus (L.)

Summary Monarch butterflies, Danaus plexippus (L.), display a warm-up behavior characterized by wingstrokes of small amplitude. Thoracic temperature during this shivering and during fixed flight was measured by means of a smallbead thermistor inserted into the thorax. At ambient temperatures of 15–16°C, once shivering is initiated the thoracic temperature rises at a maximum rate of 1.3°C/min, and a thoracic temperature 4.0°C greater then ambient is produced (Table 1). Fixed flight at these low ambient temperatures results in a similar rate of increase in thoracic temperature, and a similar temperature excess is produced (Fig. 3). At ambient temperatures between 22 and 35°C the thoracic temperature of an animal starting to fly rises at a faster rate, 3.6°C/min, and reaches a greater excess, 7.9°C (Fig. 4). The wingbeat frequency of animals in fixed flight increases with increasing thoracic temperature (Fig. 2). In the absence of direct solar radiation, shivering typically occurs prior to flight at low ambient temperatures (13–17°C), and the resulting increase in thoracic temperature allows monarch butterflies to fly at these cool temperatures.I thank Miss Janice Ruppert and Mr. C. J. Doughty for their valuable technical assistance. The co-operation of the administrators of New Brighton Beach State Park in permitting me to collect in the park is appreciated. Financial support for this study was provided in part by a faculty research grant from the University of California.     

Germination characteristics ofDiamorpha cymosa seeds and an ecological interpretation

Summary Laboratory-stored seeds ofDiamorpha cymosa (Nutt.) Britton (Crassulaceae) were germinated at monthly intervals starting shortly after maturity in late May and ending at approximately the time germination is completed in the field (November). Seeds were placed at 5, 10, 15, 20, 25, 30, 15/6, 20/10, 30/15 and 35/20°C at a 14-hr photoperiod (12/12 hr thermoperiods at the alternating temperature regimes) and in constant darkness. In June, seeds were almost completely dormant and thus germinated poorly or not at all under all conditions. As seeds aged from late May to November 1. germination at the 14-hr photoperiod increased in rate and total percentage, 2. the maximum germination temperature increased from 15 to 25°C at constant temperatures and from 20/10 to 30/15°C at the alternating temperature regimes and 3. the optimum temperature for germination increased from 15 to 15–20°C at constant temperatures but remained at20/10°C at alternating temperature regimes throughout the study. During the same period germination in constant darkness was negligible at constant and alternating temperature regimes. This pattern of physiological after-ripening apparently is an adaptation to summer-dry,winter-wet habitats such as rock outcrops of southeastern United States.A short period of illumination with white light given after a 12-hr imbibition period in darkness promoted germination in the dark at 25/10°C but not at 15 or 25°C. A short period of illumination given during the imbibition period was much less effective in promoting germination in the dark. Drying up to 7 days did not cause light-stimulated seeds to lose their ability to germinate in darkness. The light requirement for seed germination probably does not play a role in restrictingD. cymosa to its well-lighted habitats on granite and sandstone outcrops.This research was supported by funds from the University of Kentucky Research Foundation and by an NIH Biomedical Sciences Support Grant to the University of Kentucky.     

Effect of cooling rate,cryoprotectant and holding time at different transfer temperatures on the survival of cryopreserved cell suspension culture (Puccinellia distans (L.) Parl.)

Reflexed saltmarsh-grass suspension cultures produced by seed callus were frozen to the liquid nitrogen temperature. Cooling rates, cryoprotectants and holding times were taken as a function of transfer temperatures. The highest survival of cells (45%) was found at a freezing rate of 1°C min^-1, without cryoprotectant treatments. The cryoprotectants (proline, dimethyl sulphoxide, glycerol), used at different concentrations and transfer temperatures, increased the survival rate. The maximum value was 78% at 12.5% (w/v) of proline with –30°C transfer temperature. Considerable improvement of viability (from 0% to 95%) among the 12.5 and 15.0% (v/v) dimethyl sulphoxide cryopreserved cells was achieved by holding them at – 20°C for 10–30 min before plunging into the liquid nitrogen. A 20 min holding time at 15.0% (v/v) glycerol level and – 30°C transfer temperature significantly enhanced the viability of the explants from 42% to 92%. Plants were successfully regenerated from cells cryopreserved with proline (w/v) and dimethyl sulfoxide (v/v) levels of 12.5 and 15.0%, respectively.     

Immunochemical analysis of trichothecenes produced by various fusaria

The production of type A trichothecene mycotoxins by 19 Fusaria, including 12Fusarium sporotrichioides, 4F. chlamydosporum and 3F. graminearum at 15°C and 25°C over a 35-day period was analyzed by ELISA using antibodies cross-reactive with most type A trichothecenes after conversion to T-2 tetraol tetraacetate. The toxin production peaked at 20–25 days of incubation with maximum yield between 4–6 mg type A trichothecene/ml of culture medium for 5F. sporotrichioides cultures and between 1 to 2 mg/ml for 6F. sporotrichioides cultures. OneF. sporotrichioides produced 700 µg type A trichothecenes/ml of culture medium. Detectable type A trichothecene was also found in the culture extracts ofF. chlamydosporum andF. graminearum, but the yield was very low (less than 100 µg/ml). Quantitative determination of individual trichothecenes was achieved by separation of different toxin in HPLC and followed by ELISA analysis. Eight to 10 immunoreactive peaks, corresponding to various type A trichothecenes, were detected in all the fungal extracts. T-2 tetraol (T-2-4ol), 4-acetyl-T-2 tetraol (4-Ac-T-2-4ol), neosolaniol (NEOS), diacetoxyscirpenol (DAS), HT-2 and T-2 toxin accounted for more than 85% of the total toxins. In general, low temperature was preferred for total type A trichothecene production. More T-2-4ol, 4-Ac-T-2-4ol, HT-2 and DAS were produced at 25°C. In contrast, more T-2 toxin and NEOS were produced at 15°C. Transformation of T-2 toxin and NEOS to polar metabolites such as T-2-4ol, 4-acetyl-T-2-4ol and HT-2 by various strains were observed at both temperatures after 25 days incubation.     

Behaviour of proteolytic Clostridium botulinum types A and B near the lower temperature limits of growth

Summary The behaviour of spores of Clostridium botulinum type A and proteolytic C. botulinum type B has been studied in cooked meat medium at 10°C, 12°C, 15°C, and 20°C, using mixed cultures (9 groups of in total 41 strains) and pure cultures (41 strains).At 10°C a decrease of 1–1.5 log cycles for type B and of 2–4 log cycles for type A Clostridia was observed. Neither growth nor toxin formation could be demonstrated.At 12°C spores of some strains developed and formed toxin with 3–4 weeks, whereas other strains did not develop within 7 weeks.At 15°C growth and toxin formation could be observed within 1 week, whereas at 20°C toxin was formed mostly within 2 or 3 days. Incubation at 10°C prior to incubation at 20°C seemed to have some effect on the lag time.